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Weather & Climate in Hartley, CA
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Hartley enjoys a temperate climate with an average annual temperature of 64°F (18°C). Winters average 49°F in January while summers reach 79°F in July. The area gets 326 sunny days per year, well above the U.S. average of 205 / making it one of the sunnier locations in the country. Annual precipitation totals 25.6 inches (drier than the 38-inch national average). Air quality is rated Good with a median AQI of 48. The city sits at an elevation of 130 feet.
Temperature
49°F Jan (9°C)
79°F Jul (26°C)
| Annual Average | 63.6°F |
| 18% above US avg | |
| January Average | 49°F (9°C) |
| July Average | 79°F (26°C) |
| Sunny Days | 326 days/yr |
Geography
| Elevation | 130 ft (40 m) |
| Area | 6.5 sq mi (16.8 km²) |
| Population Density | 304/sq mi |
| Coordinates | 38.4204°N, 121.9508°W |
| Timezone | America/Los_Angeles |
| County | Solano County County |
| Nearest Airport | Sacramento International (SMF) 27 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 48.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Relatively High |
| Risk Score | 97.0 / 100 |
| Social Vulnerability | 25.2 / 100 |
| Community Resilience | 71.8 / 100 |
Hazard Breakdown
| Tornado | Relatively Low |
| Earthquake | Relatively High |
| Wildfire | Relatively Moderate |
| Flood | Relatively High |
| Hail | Very Low |
| Strong Wind | Relatively Low |
| Heat Wave | Relatively Low |
| Winter Weather | Very Low |
| Lightning | Relatively Moderate |
| Drought | Relatively High |
| Cold Wave | No Rating |
| Landslide | Relatively High |
| Coastal Flood | Relatively High |
| Tsunami | Very Low |
| Volcano | Very Low |
| Avalanche | Very Low |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Earthquake History
4,221 earthquakes (M2.5+) recorded within 150 km since 1990. Strongest on record: M6.0.
| Aug 24, 2014 | The 2014 South Napa, California Earthquake | M6.0 | 39 km | 11 km |
| Aug 10, 2016 | 20 km NNE of Upper Lake, California | M5.1 | 125 km | 14 km |
| Sep 3, 2000 | 5 km WSW of Yountville, California | M4.9 | 41 km | 9 km |
| Sep 4, 1995 | 13 km SW of Middletown, California | M4.8 | 75 km | 7 km |
| May 12, 2006 | 7 km W of Cobb, California | M4.7 | 87 km | 4 km |
| May 21, 1996 | 8 km ESE of East Foothills, California | M4.7 | 120 km | 8 km |
| Aug 11, 1993 | 14 km ESE of Alum Rock, California | M4.7 | 126 km | 9 km |
| Jan 2, 2025 | 4 km NW of Cobb, CA | M4.7 | 84 km | 1 km |
| Aug 18, 1999 | 0 km S of Bolinas, California | M4.6 | 86 km | 8 km |
| Jan 11, 2000 | 6 km N of Geyserville, California | M4.6 | 92 km | 6 km |
| Feb 18, 2004 | 4 km WNW of Cobb, California | M4.6 | 85 km | 3 km |
| Sep 19, 2023 | 15 km SW of Westley, CA | M4.5 | 123 km | 4 km |
| Jan 12, 2014 | 8 km W of Cobb, California | M4.5 | 87 km | 2 km |
| Sep 25, 2012 | 3 km N of Talmage, California | M4.5 | 134 km | 11 km |
| Aug 3, 2006 | 5 km W of Glen Ellen, California | M4.5 | 56 km | 9 km |
| Jun 8, 2024 | 7 km NW of The Geysers, CA | M4.5 | 87 km | 4 km |
| Sep 19, 1992 | 7 km NW of Cobb, California | M4.5 | 88 km | 3 km |
| Apr 24, 2007 | 7 km WSW of Cobb, California | M4.5 | 84 km | 2 km |
| Jun 3, 2023 | 2km NW of The Geysers, CA | M4.5 | 83 km | 4 km |
| Mar 14, 2013 | 5 km W of Cobb, California | M4.4 | 85 km | 1 km |
Source: USGS Earthquake Catalog (M2.5+, 1990-2025). Sorted by magnitude.
Tornado History
82 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF2. Total: 1 injury.
| Date | Rating | Distance | Path | Fatalities |
| Feb 7, 1978 | EF2 | 54 km | 1.9 mi | 0 |
| Jun 1, 1958 | EF2 | 91 km | 15.0 mi | 0 |
| Dec 24, 2015 | EF1 | 79 km | 6.2 mi | 0 |
| Oct 22, 2012 | EF1 | 77 km | 2.0 mi | 0 |
| Oct 22, 2012 | EF1 | 82 km | 0.3 mi | 0 |
| Mar 18, 2011 | EF1 | 66 km | 0.1 mi | 0 |
| Jan 23, 2010 | EF1 | 59 km | 1.6 mi | 0 |
| Mar 20, 2005 | EF1 | 95 km | 3.0 mi | 0 |
| Dec 5, 1998 | EF1 | 65 km | 1.5 mi | 0 |
| Dec 23, 1996 | EF1 | 88 km | 6.0 mi | 0 |
| Feb 22, 1996 | EF1 | 69 km | 1.0 mi | 0 |
| Dec 2, 1992 | EF1 | 77 km | 1.0 mi | 0 |
| Dec 2, 1992 | EF1 | 83 km | 7.5 mi | 0 |
| Dec 2, 1992 | EF1 | 77 km | 3.0 mi | 0 |
| Apr 19, 1988 | EF1 | 75 km | 0.2 mi | 0 |
| Apr 19, 1988 | EF1 | 74 km | 1.0 mi | 0 |
| Mar 22, 1983 | EF1 | 62 km | 2.0 mi | 0 |
| Feb 27, 1983 | EF1 | 65 km | 0.8 mi | 0 |
| May 31, 1967 | EF1 | 76 km | 0.1 mi | 0 |
| Nov 10, 1964 | EF1 | 75 km | 1.0 mi | 0 |
Source: NOAA Storm Prediction Center (EF0+, 1950-2024, US only).
Tsunami History
4 tsunamis recorded within 500 km. Highest wave on record: 4.5 m (15 ft).
| Year | Location | Cause | Max Wave | Deaths | Distance |
| 1868 | N. CALIFORNIA | Eruption + Earthquake | 4.5 m | 30 | 81 km |
| 1856 | N. CALIFORNIA | Eruption + Earthquake | 0.6 m | - | 107 km |
| 1906 | N. CALIFORNIA | Eruption + Earthquake | 0.1 m | - | 93 km |
| 1865 | N. CALIFORNIA | Eruption + Earthquake | - | - | 136 km |
Source: NOAA/NCEI Historical Tsunami Database.
Nearby Volcanoes
1 volcano within 200 km. Closest: Clear Lake (94 km).
| Name | Type | Elevation | Last Eruption | Distance |
| Clear Lake | Volcanic field | 1,439 m (4,721 ft) | Unknown | 94 km |
Source: Smithsonian Institution Global Volcanism Program (GVP).
Wildfire History
20 wildfires (100+ acres) recorded within 100 km. Largest: HENNESSEY (314,241 acres, 2020).
| Year | Name | Acres Burned | Distance |
| 2020 | HENNESSEY | 314,241 | 37 km |
| 2015 | ROCKY | 96,125 | 70 km |
| 2018 | COUNTY | 92,450 | 34 km |
| 2019 | KINCADE | 77,780 | 77 km |
| 2015 | VALLEY | 77,507 | 71 km |
| 2020 | GLASS | 68,020 | 54 km |
| 2017 | NUNS | 56,883 | 49 km |
| 2020 | WALLBRIDGE | 55,194 | 95 km |
| 2017 | ATLAS | 51,664 | 26 km |
| 2004 | RUMSEY | 39,335 | 47 km |
| 1999 | SIXTEEN | 37,162 | 54 km |
| 2017 | TUBBS | 36,981 | 66 km |
| 1988 | MILLER | 35,750 | 13 km |
| 2017 | 18,691 | 90 km | |
| 2012 | SIXTEEN COMPLEX | 18,191 | 72 km |
| 2024 | CORRAL | 16,138 | 97 km |
| 2006 | ZAM ASSIST | 14,404 | 37 km |
| 2008 | WALKER | 12,441 | 85 km |
| 2004 | GEYSERS | 12,075 | 77 km |
| 1995 | VISION | 11,931 | 90 km |
Source: NIFC/IRWIN Wildfire Records (100+ acres).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 49°F (9°C) | 5.1 in | Wettest |
| February | 51°F (10°C) | 4.3 in | |
| March | 55°F (13°C) | 3.3 in | |
| April | 59°F (15°C) | 1.0 in | |
| May | 66°F (19°C) | 0.5 in | |
| June | 72°F (22°C) | 0.1 in | |
| July | 79°F (26°C) | 0.0 in | Warmest, Driest |
| August | 74°F (23°C) | 0.0 in | |
| September | 71°F (22°C) | 0.3 in | |
| October | 64°F (18°C) | 1.1 in | |
| November | 53°F (12°C) | 3.0 in | |
| December | 46°F (8°C) | 3.4 in | Coldest |
Hartley has a seasonal temperature swing of 33°F / from 46°F in December to 79°F in July. Total annual precipitation is 22.2 inches, with January being the wettest month (5.1") and July the driest (0.0").